1. Field of the Invention
This invention relates to systems for eliminating interference in receiver signals from adjacent transmitters, for example, for eliminating transmitted radar jamming signals from a receiver on an airplane.
2. Description of the Prior Art
In situations where a receiver antenna must be located near to a transmitter antenna, such as on an airplane, the transmitted signal is picked up by the receiver antenna reducing the sensitivity of the receiver. One technique for eliminating the interfering transmitter signal from the receiver is to insert a cancellation signal derived from the transmitter signal into the receiver input with opposite phase to cancel the interfering signal. However, the cancellation signal derived from the transmitter and the interfering signal from the transmitter take different paths through different media, such as free space, wave guide, coaxial cable, etc., and the velocities of propagation in these media do not all vary in the same way as a function of the transmitter frequency. Thus for frequency varying transmitters, the delay of the cancellation signal will not correspond to the delay of the interfering signal for a certain portion of the interfering signal, preventing the cancellation thereof.